Immersion lithography apparatus and method having movable liquid diverter between immersion liquid confinement member and substrate

ABSTRACT

An immersion lithography apparatus that includes a substrate holder on which a substrate is held, a projection system having a final optical element and that projects an exposure beam onto the substrate through an immersion liquid, and a liquid confinement member having an aperture through which the exposure beam is projected, a lower surface including a non-fluid removal area surrounding the aperture, and a liquid recovery outlet from which the immersion liquid is recovered, also includes a movable member. The movable member is movable relative to the liquid confinement member in a substantially horizontal direction, and has an opening through which the exposure beam is projected. The movable member has upper and lower surfaces that surround the opening, and is movable while a portion of the upper surface faces the non-fluid removal area in the lower surface of the liquid confinement member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 12/382,100filed Mar. 9, 2009 (now U.S. Pat. No. 8,610,873), which claims thebenefit of U.S. Provisional Patent Application No. 61/064,630 filed Mar.17, 2008, U.S. Provisional Patent Application No. 61/071,098 filed Apr.11, 2008, and U.S. Provisional Patent Application No. 61/193,350 filedNov. 20, 2008. The disclosure of each of these applications isincorporated herein by reference in its entirety.

BACKGROUND

The invention relates to immersion lithography apparatus and methods,and particularly to apparatus and methods for controlling the immersionliquid between the projection system and the substrate.

A typical lithography apparatus includes a radiation source, aprojection optical system and a substrate stage to support and move asubstrate to be imaged. A radiation-sensitive material, such as aresist, is coated onto the substrate surface before the substrate isplaced on the substrate stage. During operation, radiation energy fromthe radiation source is used to project an image defined by an imagingelement (such as, for example, a mask) through the projection opticalsystem onto the substrate. The projection optical system typicallyincludes a plurality of lenses. The lens or optical element closest tothe substrate can be referred to as the last or final optical element.

The projection area during an exposure is typically much smaller thanthe imaging surface of the substrate. The substrate therefore has to bemoved relative to the projection optical system to pattern the entiresurface of the substrate. In the semiconductor industry, two types oflithography apparatus are commonly used. With so-called “step andrepeat” apparatus, the entire image pattern is projected at once in asingle exposure onto a target area of the substrate. After the exposure,the wafer is moved or “stepped” in the X and/or Y direction and a newtarget area is exposed. This step and repeat process is performed overand over until the entire substrate surface is exposed. With scanningtype lithography apparatus, the target area is exposed in a continuousor “scanning” motion. The imaging element is moved in one direction,while the substrate is moved in either the same or the oppositedirection during exposure. After each scan, the substrate is then movedin the X and/or Y direction to the next scan target area. This processis repeated until all the desired areas on the substrate have beenexposed.

Lithography apparatus are typically used to image or patternsemiconductor wafers and flat panel displays. The term “substrate”, asused herein, is intended to generically mean any work piece that can bepatterned, including, but not limited to, semiconductor wafers and flatpanel displays.

Immersion lithography systems use a layer of fluid that fills a gapbetween the final optical element of the projection optical system andthe substrate. The fluid enhances the resolution of the system byenabling exposures with a numerical aperture (NA) greater than one,which is the theoretical limit for conventional “dry” lithography. Thefluid in the gap permits the exposure with radiation that wouldotherwise be completely internally reflected at the optical-airinterface. With immersion lithography, numerical apertures as high asthe index of refraction of the fluid are possible. Immersion alsoincreases the depth of focus for a given NA, which is the tolerableerror in the vertical position of the substrate, compared to aconventional dry lithography system. Immersion lithography therefore hasthe ability to provide greater resolution than can be performed usingconventional dry lithography, as the fluid essentially becomes part ofthe optical system of the lithography apparatus.

One known way of maintaining the immersion fluid in the gap whereexposure of the substrate is to occur is with the use of an air curtain.For more information on air curtain type immersion apparatus, see forexample U.S. Patent Publication No. 2005/0007569, the disclosure ofwhich is incorporated herein by reference in its entirety.

It is also known to maintain the immersion fluid in the gap between thefinal optical element and the imaging surface of the substrate bysubmersing both in a container filled with immersion fluid. See, forexample, U.S. Pat. No. 4,509,852, the disclosure of which isincorporated herein by reference in its entirety.

Another known way of maintaining the immersion fluid within the gap ofan immersion lithography apparatus is with the use of a confinementmember that surrounds the final optical element immediately above thearea to be exposed on the substrate. For more information on confinementmember type immersion lithography apparatus, see U.S. Pat. No. 7,292,313and WO 2005/111722, the disclosure of each of which is incorporatedherein by reference in its entirety.

In yet another approach, which is a variation of the above-describedsubmersion type apparatus, a large confinement plate is used forsubmerging the substrate to be imaged in the immersion fluid. For moredetails on confinement plate type immersion lithography apparatus, seeU.S. Patent Publication No. 2007/0279608, the disclosure of which isincorporated herein by reference in its entirety.

During semiconductor wafer fabrication, for example, wafers aretypically patterned one after another by the lithography tool. After awafer has been patterned, it is replaced and the next wafer is exposed.This process is completed over and over, typically as fast as possible,to increase throughput. During a wafer exchange, the just exposed wafertypically has to be moved a relatively long distance from the exposurearea to the wafer exchange area. This movement preferably is performedat a relatively high speed. Once the exchange takes place, the new waferundergoes another relatively long-move to an alignment area. Thismovement also preferably is performed at a relatively high speed. Afteralignment, the wafer undergoes yet another long-move back to theexposure area for exposure. This movement also preferably is performedat a relatively high speed. For the sake of simplicity, all of theabove-described moves are hereafter generically referred to as“long-moves”.

It also is desirable to move from target area to target area on asubstrate during the exposure operation at a relatively high speed.Furthermore, when exposure of a target area begins in a scanningexposure apparatus, it is desirable to accelerate at as high a rate aspossible at the beginning of the scanning movement and to scan acrossthe target area during exposure of the target area at as high a speed aspossible.

High speed movements are desirable in order to increase the throughput(the rate of production) of the exposure process performed by thelithography apparatus.

High speed moves can be problematic with confinement member typeimmersion apparatus. In particular, if the speed is too fast, there is atendency for the immersion fluid to leak out from under the confinementmember, leaving a trail of water (or other liquid if a liquid other thanwater is used as the immersion fluid) behind on the substrate. Liquidthat escapes from the liquid confinement member also can scatter insidethe exposure apparatus, which can deteriorate components of the exposureapparatus and/or adversely change the environmental conditions (forexample, temperature and humidity) within the apparatus.

U.S. Patent Publication No. 2007/0110213 discloses a plate disposed on abarrier member that confines a liquid between the projection system andthe substrate. The plate separates the liquid-filled space between thebarrier member and the substrate into upper and lower channels, suchthat a meniscus is formed in each of the channels.

SUMMARY

According to a first aspect of the invention, a movable liquid diverteris positioned between a liquid confinement member and a substrate (orother object that may be located below the projection system andconfinement member) in an immersion lithography apparatus. The apparatusincludes a substrate holder on which the substrate having an imagingsurface is held, and a projection system having a final optical element.The projection system projects an image onto a target imaging area onthe imaging surface of the substrate held on the substrate holderthrough an immersion liquid that is filled in a gap between the imagingsurface of the substrate and the final optical element. The liquidconfinement member maintains the immersion liquid in the gap between theimaging surface of the substrate and the final optical element. Theimmersion liquid has a meniscus where the immersion liquid is in contactwith ambient gas. The meniscus defines a footprint of the immersion areaof the immersion liquid.

The movable liquid diverter is movable relative to the liquidconfinement member in a direction parallel to the imaging surface of thesubstrate. The movable liquid diverter includes an opening thatsurrounds the immersion area. The opening can contact the liquid in theimmersion area or it can be slightly spaced from the liquid in theimmersion area (that is, the opening can be slightly spaced from themeniscus) when the substrate holder is stationary.

The movable liquid diverter moves in a same direction as the substrateholder (and the held substrate) when the substrate holder moves thesubstrate in a direction parallel to the imaging surface. Preferably,the liquid diverter is moved at a speed that is slower than a speed atwhich the substrate holder moves. Preferably, the liquid diverter ismoved by an amount that is less than an amount by which the substrateholder moves. Moving the liquid diverter when the substrate holder ismoved functions to reduce (or preferably prevent) liquid from beingscattered from between the liquid confinement member and the substratesurface when the substrate is moved.

This aspect of the invention is particularly helpful in preventingscattering of liquid during high-speed movements of the substrateholder. Thus, according to some embodiments, the liquid diverter only ismoved when the substrate holder is moved at a speed higher than apredetermined speed. Such a movement reduces the relative difference inspeed between the liquid and the surfaces contacted by the liquid.

The apparatus can include a drive system such as an actuator coupled tothe liquid diverter so as to move the liquid diverter. The drive systemcan be a voice coil motor, a Lorentz-force actuator or other actuatorsthat are capable of moving the liquid diverter by a suitable distance.

The liquid diverter can be a single plate having an opening or it can bea plurality of plates that collectively define the opening.

The opening of the liquid diverter is larger than the liquid confinementmember aperture (through which an exposure beam is being projected) sothat movement of the liquid diverter does not block the exposure beam.

According to some embodiments, the liquid diverter has a surface with anarea larger than the liquid confinement member aperture so that theliquid diverter can function as a shutter or cover plate that blocks theliquid confinement member aperture to maintain liquid between theprojection system final optical element and the liquid confinementmember, for example, when the substrate holder is moved away from theprojection system during substrate exchange, etc.

According to another aspect of the invention, movement of the substrateholder (or other object located below the projection system and liquidconfinement member) can be used to enhance the shutter-insertionprocess. For example, the substrate holder can be moved in a directionparallel to the substrate surface prior to insertion of the shutter(whether the shutter be the liquid diverter or a dedicated shutter) sothat the meniscus on one side of the liquid confinement member apertureis moved to a position closely adjacent to the edge of the aperture. Theshutter then is moved in the same direction as the substrate holderwhile the substrate holder continues to move, to insert the shutterbetween the liquid confinement member aperture and the substrate holder.This improves the removal of liquid from the substrate surface (i.e.,from beneath the shutter or from between the shutter and the substratesurface) at a position downstream of the shutter relative to the motiondirection of the shutter.

Preferably, the shutter is shaped to have a size such that it does notcover the liquid recovery portion on the lower surface of the liquidconfinement member (or a size that covers only a part of the liquidrecovery portion) when the shutter is in the position at which itcompletely covers the liquid confinement member aperture. This enablesthe liquid recovery portion to efficiently recover liquid remaining onthe substrate surface once the liquid confinement member aperture iscovered.

According to some embodiments, the shutter is positioned so that aleading edge of the shutter is located adjacent to the edge of theliquid confinement member aperture just as the previously-conductedexposure operation is completed so that insertion of the shutter overthe liquid confinement member aperture can start as quickly as possibleafter the completion of an exposure operation on a substrate.

According to another aspect of the invention, after the shutter ispositioned over the aperture by moving the shutter in one direction (forexample, the X direction) parallel to the substrate surface, thesubstrate table is moved in a direction perpendicular to the directionin which the shutter was moved but parallel to the substrate surface(for example, the Y direction) so as to cause liquid present below theshutter to move to a corner of the shutter. The liquid collected nearthe corner of the shutter can be more easily recovered, for example, byproviding the corner of the shutter with a shape that will causecollected liquid to easily flow to the liquid recovery portion disposedon the lower surface of the liquid confinement member.

According to another aspect of the invention, the substrate holder (orother object disposed below the projection system and liquid confinementmember) can be moved in a direction that assists in reducing theformation of bubbles when the shutter is removed from its position overthe liquid confinement member aperture. For example, the substrate tablecan be moved in the same direction in which the shutter is moved away asthe shutter moves away from its position covering the liquid confinementmember aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of an immersion lithography apparatus according toone embodiment of the invention;

FIG. 1B is a diagram illustrating the meniscus footprint of theimmersion liquid disposed between a substrate and the liquid confinementmember;

FIG. 2A is a top perspective view of a liquid confinement memberaccording to one embodiment of the invention;

FIG. 2B is a bottom perspective view of the FIG. 2A liquid confinementmember and also shows a movable liquid diverter;

FIG. 3 is a cross section view of a liquid diverter according to a firstembodiment positioned so that its opening is spaced from the meniscusformed between a liquid confinement member and a substrate when thesubstrate is stationary;

FIG. 4 is a cross section view of the FIG. 3 system and shows how theliquid diverter moves when the substrate is moved;

FIG. 5 is a cross section view of a liquid diverter according to anotherembodiment in which an edge of the opening of the liquid divertercontacts the meniscus formed between the liquid confinement member andthe substrate when the substrate is stationary;

FIG. 6 is a cross section view of the FIG. 5 embodiment and shows howthe liquid diverter moves when the substrate moves;

FIG. 7 is a cross section view of an embodiment that includes a slopedliquid diverter;

FIG. 8 is a cross section view of an embodiment in which the liquiddiverter has a protrusion formed on its lower surface around the openingin the liquid diverter;

FIGS. 9A-9C are cross section views of the liquid diverter used as ashutter or closing plate to maintain liquid in contact with theprojection system final optical element, for example, during substrateexchange;

FIGS. 10A-10E are cross section views showing a process for inserting ashutter between the liquid confinement member and the substrate, and forremoving the shutter from that position; and

FIGS. 11A and 11B are flow diagrams illustrating the sequence offabricating semiconductor wafers according to an aspect of theinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring to FIG. 1A, an immersion lithography apparatus is shown. Theimmersion lithography apparatus 10 includes an imaging element 12 whichdefines an image, a projection optical system 14 which includes a “last”or “final” optical element 16, a liquid confinement member 18, a coarsestage 20, a fine stage 22, and a substrate chuck 24 for holding asubstrate 26, and a space 28 under the final optical element 16 and theliquid confinement member 18. The space 28 includes a gap providedbetween the top surface of the substrate 26 and the final opticalelement 16, when the final optical element 16 and the top surface of thesubstrate 26 are opposite to each other. In one embodiment, the liquidconfinement member 18 is a confinement member by which the gap betweenthe substrate 26 and the final optical element 16 is filled with animmersion fluid 29 (not visible in FIG. 1A). Again, for more informationon confinement member type immersion lithography apparatus, see U.S.Pat. No. 7,292,313 and WO 2005/111722, the disclosures of which areincorporated herein by reference in their entireties.

Referring to FIG. 1B, a top-down view of the immersion fluid 29 betweenthe liquid confinement member 18 and the final optical element 16 on oneside and the substrate 26 on the other side is shown. In one embodiment,the immersion fluid 29 is a liquid, such as water. The perimeter or themeniscus 30 of the immersion fluid 29, which is defined as the interfacewhere the immersion fluid 29 is in contact with the ambient gas, definesa “footprint” or an outer shape of the body of fluid 29 under the liquidconfinement member 18. When the substrate 26 is moved, during a long,high-speed move for example, the meniscus 30 of the body of fluid 29 maybe altered in an undesirable way. It should be noted that the diagram ofFIG. 1B is for illustrative purposes, and is not necessarily drawn toscale. Also a number of elements, such as the remainder of theprojection optical system 14 and the substrate chuck 24, are not shownfor the sake of clarity.

The present embodiment is directed to a movable liquid diverter 60positioned under the liquid confinement member 18. The movable liquiddiverter 60, as described in detail below, is configured to alter orcontrol the footprint shape of the body of immersion fluid 29particularly during relatively high speed movements of the substrate 26.The diverter 60 can help to prevent the formation of fingers ofimmersion fluid from the immersion area and minimize (preferablyprevent) leakage of immersion fluid from between the liquid confinementmember 18 and the substrate. In the following explanation, although thesubstrate 26 is positioned or moved under the liquid confinement member18 and the optical element 16, an object other than the substrate 26 canbe positioned or moved under the liquid confinement member 18 and theoptical element 16. The object could be, for example, a measurementstage having measuring devices provided on an upper surface thereof.

Referring to FIGS. 2A-2B, top and bottom perspective views of the liquidconfinement member 18 with a movable liquid diverter 60, according toone embodiment, are shown. In this embodiment, the movable liquiddiverter 60 is a single plate 62 having a central opening 64. However,the invention is not limited to the illustrated configuration. Forexample, the movable liquid diverter 60 could be formed from a pluralityof separately movable and controllable plates. For example, fourrectangular plates, one on each of the four sides of the opening 64could be provided. Alternatively, two L-shaped plates could be provided,with each of the plates extending along two adjacent sides of theopening 64. The shape of the plate(s) and opening formed by the platesneed not be rectangular.

FIG. 2A shows a top-down perspective view of the liquid confinementmember 18. The liquid confinement member 18 includes a top plate 32, abottom plate 44 and a recess 34. A part of the final optical element 16is positioned within the recess 34 (for the sake of clarity, theremainder of the projection optical system 14 is not illustrated). Theliquid confinement member 18 also includes at least one fluid supplyinlet 36 and outlet 38 for supplying and recovering the immersion fluidrespectively. Again for the sake of simplicity, only one inlet 36 andoutlet 38 is shown. In alternative embodiments, a plurality of inlets 36and outlets 38 may be used.

FIG. 2B shows a bottom-up perspective view of the liquid confinementmember 18, including a liquid recovery portion 42 provided on the bottomplate 44. As illustrated in this view, the liquid recovery portion 42 isprovided between the bottom plate 44 of the liquid confinement member 18and the liquid diverter 60. The liquid confinement member 18 (the bottomplate 44) includes an aperture 54, which is positioned at the center ofthe bottom plate 44 and under the final optical element 16, and throughwhich the image is projected onto the top surface of the substrate 26.The liquid confinement member 18 (the bottom plate 44) includes anon-fluid removal area 56 which surrounds the aperture 54. The non-fluidremoval area 56 is provided for containing the immersion fluid 29. Theliquid recovery portion 42 is provided further away from the aperture 54than the non-fluid removal area 56. In this embodiment, the liquidrecovery portion 42 surrounds the non-fluid removal area 56. The liquidrecovery portion 42 has a bottom surface that partially faces the liquiddiverter 60. In this embodiment, the bottom surface of the liquidrecovery portion 42 is substantially co-planar with the surface of thenon-fluid removal area 56. In one embodiment, the bottom surface of theliquid recovery portion 42 may not be co-planar with the surface of thenon-fluid removal area 56. For example, the bottom surface of the liquidrecovery portion 42 may be provided further away from the top surface ofthe substrate 26 than the non-fluid removal area 56. The liquid recoveryportion 42 is configured to contain and remove the immersion fluid 29.

The liquid diverter 60 is provided under the liquid confinement member18 (i.e., between the liquid recovery portion 42 and the substrate 26).In the illustrated embodiment, the liquid diverter 60 is a singlerectangular plate 62 having a rectangular, central opening 64. As isapparent from FIG. 2B, the size of opening 64 is larger than the size ofaperture 54 in the liquid confinement member 18. The opening 64 islarger than the aperture 54 so that when the liquid diverter 60 moves inthe direction parallel to the surface of substrate 26, the opening 64does not block the exposure beam that is being projected through theprojection system 14 and the aperture 54. Thus, during an exposureoperation, liquid diverter 60 will move by no more than an amount thatwould cause the edge of opening 64 to align with the edge of aperture54.

The liquid diverter 60 could be mounted to the liquid confinement member18. The liquid confinement member preferably is mounted to a supportmember within the exposure apparatus 10, the support member beingdifferent from a support member that supports the projection system 14so that vibrations of the liquid confinement member 18 are nottransmitted to the projection system 14. The liquid diverter 60 alsocould be mounted to the support member that supports the liquidconfinement member 18 instead of being mounted to the liquid confinementmember 18.

In some embodiments, the lower surface of the liquid diverter 60 isparallel to the upper surface of substrate 26. However, it is notnecessary for the lower surface of liquid diverter 60 to be parallel tothe upper surface of the substrate 26. For example, as shown in FIG. 7,the diverter 60′ may be sloped relative to the upper surface of thesubstrate 26 such that the lower surface of diverter 60′ slopes upwardlysuch that the distance between the lower surface of liquid diverter 60′and the substrate 26 increases as one moves farther away from theopening 64. The sloped diverter 60′ helps to center the meniscus. Asshown in FIG. 8, it also is possible to provide a protrusion (such as,for example, a step 61) on the lower surface of liquid diverter 60″around the opening 64 in order to help define the footprint of theimmersion liquid between the substrate 26 and the liquid diverter 60″.

During operation, the immersion fluid 29 is introduced into the liquidconfinement member 18 through the one or more inlets 36. The fluid 29fills at least part of the space 28, including the gap between theoptical element 16 and the substrate 26 and at least part of a gapbetween the non-fluid removal area 56 and the substrate 26. The liquidrecovery portion 42 recovers the fluid 29 and passes it through the oneor more outlets 38, where it can be either discarded or reused. Invarious embodiments, the liquid recovery portion 42 can be a mesh, aporous material (porous member), or outlets. For more details of thesetypes of liquid recovery portions, see, for example, U.S. Pat. No.7,292,313, and WO 2005/111722.

FIG. 3 is a cross section view showing the immersion fluid 29 in thespace 28 between the final optical element 16, the liquid confinementmember 18 and the substrate 26. As shown in FIG. 3, the liquid diverter60 is disposed between the liquid confinement member 18 and thesubstrate 26. In the FIG. 3 embodiment, the opening 64 of the liquiddiverter 60 is spaced a small distance from the meniscus 30 that formsbetween the substrate 26 and the lower surface of the bottom plate 44 ofthe liquid confinement member 18. FIG. 3 also shows liquid inlet ports47 provided on the bottom plate 44, which supply the immersion fluid tothe space 28. FIG. 3 also shows liquid recovery outlets 49 provided inthe bottom plate 44 and which connect a chamber holding the porousmember of the liquid recovery portion 42 with, for example, a vacuum.FIG. 3 also shows a controller 100 which can be, for example, controlcircuitry or a programmed computer, which controls the movement of theliquid diverter 60. In particular, controller 100 causes actuator orother drive system 80, which is coupled to the liquid diverter 60, tomove the liquid diverter 60 as described below.

As indicated above, FIG. 3 shows the position of the liquid diverterrelative to the meniscus 30 when the substrate 26 is stationary. Whenthe substrate is moved, the liquid diverter 60 will be moved in the samedirection as the substrate 26. FIG. 4 shows such movement of the liquiddiverter 60. In particular, in FIG. 4, the substrate 26 is moved fromleft-to-right (by moving the substrate stage 20 from left-to-right) asindicated by the arrow on substrate 26. Simultaneously with thismovement, the liquid diverter 60 is moved from left-to-right asindicated by the arrow on the diverter 60. Preferably, the liquiddiverter 60 is moved by an amount and at a speed which is less than themovement amount and speed by which the substrate 26 is moved.

Moving the liquid diverter 60 as described above has been found toreduce or eliminate scattering of liquid that can be caused by highspeed movements of the substrate 26 (or other object that is being movedbelow the projection system and liquid confinement member). It isbelieved that the scattering of liquid is reduced or eliminated becausethe liquid diverter reduces the relative difference in moving speeds ofthe two surfaces between which the meniscus is formed. For example, ifno liquid diverter was provided, the relative difference in speedbetween the two surfaces between which the meniscus is formed (the twosurfaces would be the lower surface of the bottom plate 44 and the uppersurface of the substrate 26) would be equal to the movement speed of thesubstrate 26. By disposing the liquid diverter plate 60 between thelower surface of bottom plate 44 and the upper surface of substrate 26,and moving the liquid diverter in the same direction as the substratebut at a lower speed, the meniscus formed between the lower surface ofbottom plate 44 and the upper surface of liquid diverter 60 will besubjected to a surface speed differential equal to the movement speed ofthe liquid diverter 60 (which is less than the movement speed of thesubstrate 26). Similarly, the meniscus formed between the lower surfaceof the liquid diverter 60 and the upper surface of the substrate 26 willbe subjected to a surface speed differential equal to the differencebetween the substrate speed and the liquid diverter speed (which will beless than the movement speed of the substrate 26). Thus, both of themeniscus will be subjected to less force than would occur if no liquiddiverter plate was provided or if the liquid diverter plate wasstationary or moved at a speed equal to or higher than the speed atwhich the substrate is moved.

The liquid diverter 60 does not need to move by an amount equal to theamount by which the substrate 26 is moved. Rather, the liquid diverter60 can be moved by a maximum amount equal to, for example, 20-30 mm.After moving, the liquid diverter 60 can be returned to the positionshown in FIG. 3. Because it is common for substrates to be moved inalternating directions as each device region (also called a “shotregion”) is exposed, it is easily possible to implement theabove-described process because the substrate and liquid diverter wouldbe moved from left-to-right for a first device region, then moved fromright-to-left for the next device region, then moved from left-to-rightfor the next device region, and so on. For long movements of thesubstrate stage, the movement amount of the liquid diverter still iskept to no more than about 20-30 mm, which is effective at preventingscattering of liquid from between the lower surface of bottom plate 44and the upper surface of substrate 26.

As mentioned above, the actuator or drive system 80 of the liquiddiverter 60 can be, for example, a voice coil motor, a pneumaticactuator or a Lorentz force actuator since such devices are readilycapable of producing a movement of 20-30 mm. The drive does not need tobe highly accurate.

Depending on the speed at which the substrate 26 is moved, it may not benecessary to move the liquid diverter 60 while the substrate 26 ismoved. That is, because the liquid scattering problem typically does notoccur for slower movement speeds of the substrate, according to someaspects of the invention, the liquid diverter 60 remains stationaryrelative to the projection system and the liquid confinement member 18when the substrate 26 is moved at slower speeds, but is moved relativeto the projection system and the liquid confinement member when thesubstrate is moved at a speed higher than a predetermined speed. Forexample, if liquid scattering does not occur for substrate speeds below300 mm/sec, it would not be necessary to move the liquid diverter if thesubstrate is moved at speeds below 300 mm/sec. Then, when the substrate26 is moved at speeds higher than 300 mm/sec, the liquid diverter wouldbe moved. For example, in the above example in which 300 mm/sec is thethreshold for liquid scattering, when the substrate is moved at a speedof, for example, 400 mm/sec, the liquid diverter could be moved in thesame direction as the substrate but at a speed of 100 mm/sec. This wouldprevent the relative speed between two facing surfaces between which ameniscus is formed from exceeding the 300 mm/sec threshold. Thus, themovable liquid diverter 60 facilitates higher speed substrate movementsthan would be obtainable (without liquid scattering) without thediverter 60. It is noted that the speed thresholds described above aremerely examples, and will vary depending on the type of immersionliquid, the size of the gap 28 and the materials used to form (or coat)the substrate surface, the liquid diverter surfaces and the lowersurface of the bottom plate.

The surfaces of the liquid diverter can be made to be liquid-attractive(lyophilic) or liquid-repellent (lyophobic). For example, both the upperand lower surfaces of diverter 60 could be lyophilic. Alternatively,both the upper and lower surfaces of diverter 60 could be madelyophobic. As another alternative, the upper surface of the diverter 60could be made lyophilic and the lower surface made lyophobic. As anotheralternative, the upper surface of diverter 60 could be made lyophobicand the lower surface could be made lyophilic. Preferably, both theupper and lower surfaces of the diverter 60 are lyophobic so that liquiddoes not remain on the diverter 60 when it is inactive.

In the embodiments described herein, in which no air curtain is used tomaintain liquid between the liquid confinement member 18 and thesubstrate 26, a larger gap 28 can be provided between the lower surfaceof bottom/plate 44 and the upper surface of substrate 26, which makes iteasier to provide the liquid diverter 60 between the liquid confinementmember 18 and the substrate 26. For example, the distance between thelower surface of bottom plate 44 and the upper surface of substrate 26can be, for example, 1 mm.

FIG. 5 shows an embodiment similar to the FIG. 3 embodiment except thatthe opening 64 of the liquid diverter 60 is positioned so as to contactthe meniscus 30 when the substrate 26 is stationary, as shown in FIG. 5.Thus, if the liquid diverter 60 is a single plate 62 having an opening64, the FIG. 5 embodiment has a smaller opening than the FIG. 3embodiment. If the liquid diverter 60 is made from a plurality ofmovable plates, then the positioning of those plates can be controlledby controller 100 and drive system 80 so that the opening formed by theinner edges of the plates is smaller than in the FIG. 3 embodiment. Asshown in FIG. 6, when the substrate 26 is moved, the liquid diverter 60is moved in the same direction (but at a lower speed) than thesubstrate, as in the embodiment described above with respect to FIGS. 3and 4.

FIG. 7 shows an embodiment similar to the FIG. 3 embodiment except thatthe liquid diverter 60′ is sloped. A sloped liquid diverter 60′ helps tocenter the meniscus relative to the opening 64.

FIG. 8 shows an embodiment similar to the FIG. 3 embodiment except thatthe lower surface of the liquid diverter 60″ includes a protrusion 61extending around the opening 64. The protrusion 61 helps to define theshape of the meniscus.

The sloped structure of FIG. 7 or the FIG. 8 structure having aprotrusion 61 can be applied to the FIG. 5 embodiment as well as to theFIG. 3 embodiment.

FIGS. 9A-9C are cross section views showing the liquid diverter 60 usedas a shutter or cover plate to cover the opening 54 in the bottom plate44 of the immersion confinement member 18. The liquid diverter can beany of the previously described liquid diverters, and is moved by drivesystem 80 as controlled by controller 100. As shown in FIG. 9A, one sideof the liquid diverter 60 (for example, one side of the rectangularplate 62 or, if the liquid diverter is made from a plurality ofseparate, rectangular plates, then one of those plates) has a size suchthat its surface is larger than or equal in area to the non-fluidremoval area 56 formed in the bottom plate 44. This enables the liquiddiverter 60 to be used as a shutter. FIG. 9A shows the liquid diverter60 moved such that a portion of the liquid diverter 60 functions as ashutter in which liquid is maintained between the final optical element16 and the upper surface of the liquid diverter 60. As shown in FIG. 9B,after the liquid diverter 60 is moved to cover aperture 54, thesubstrate holder moves the substrate 26 (from left-to-right in FIG. 9B)so as to move the liquid disposed under the liquid diverter 60 to theright where it can be recovered by the liquid recovery portion 42located on the right side of the bottom plate 44 in FIG. 9B. FIG. 9Cshows the condition in which all liquid below the liquid diverter 60(that is, all liquid that remained on the upper surface of substrate 26)has been removed. The substrate holder then can be moved away from theprojection system so that an exposed substrate can be replaced with asubstrate that is to be exposed by the projection system.

As shown in FIG. 9A-9C, it is preferable that the size of the portion ofthe liquid diverter 60 that is used as a shutter is such that it doesnot cover the liquid recovery portion 42 when the liquid diverter 60 iscovering the bottom plate aperture 54. In the embodiment shown in FIGS.9A-9C, none of the liquid recovery portion 42 is covered by the liquiddiverter 60. It is, however, acceptable to cover part of the liquidrecovery portion 42. It is preferable that at least some of the liquidrecovery portion 42 is not covered to assist in removal of immersionliquid from the upper surface of substrate 26.

FIGS. 10A-10B illustrate a process of inserting a shutter between thebottom plate 44 of the liquid confinement member 18 and the substrate26. The shutter could be a dedicated shutter or it could be, forexample, the liquid diverter 60 described in any of the previousembodiments. This process is performed to minimize the shutter insertiontime.

FIG. 10A shows the liquid 29, including meniscus 30, formed betweenlower plate 44 and substrate 26 when the substrate 26 is stationary. Asshown in FIG. 10B, before the shutter 70 is inserted over the bottomplate aperture 54, the substrate 26 is moved (from right-to-left in FIG.10B) so that the immersion area moves from right to left such that theright side of the meniscus 30 is positioned closely adjacent to the edgeof bottom plate aperture 54 on the right side of the aperture 54. Also,the immersed footprint can be reduced to a minimum size. Then,preferably while the substrate 26 continues to move in the right-to-leftdirection, the shutter 70 is inserted between the bottom plate 44 andthe substrate 26 by also moving the shutter 70 in the right-to-leftdirection. This manner of inserting the shutter 70 helps to move much ofthe immersion liquid 29 to the left so that it can be quickly recoveredby the liquid recovery portion 42 disposed on the left side of thebottom plate 44 in FIG. 10C. Movement of the substrate 26 before andduring shutter insertion thus changes the shape of the immersion liquidbody so as to aid in liquid recovery.

In the above-described shutter insertion process, it is also desirableto place the shutter 70 at a position where its leading edge is alignedwith an edge of the aperture 54 just as the preceding exposure operationis completed. This enables insertion of the shutter 70 over the aperture54 to begin immediately upon completion of the exposure of the last shotregion on the substrate 26. Thus, for example, in the previous example,the leading edge (the left edge) of the shutter 70 would be locatedbelow the right edge of aperture 54 in FIGS. 10A and 10B. It isparticularly easy to do this when the liquid diverter 60 is used as ashutter because the liquid diverter 60 will be close to this positionduring its normal operation.

FIG. 10D shows the final position of the shutter 70 in which the bottomplate aperture 54 is completely covered. Preferably, after the shutter70 reaches the position shown in FIG. 10D, the substrate then is movedin a direction perpendicular to the right-to-left position (that is, ina direction that would extend into and out of the page). This causesliquid that may exist between the lower surface of shutter 70 and theupper surface of substrate 26 to be moved to a corner of the shutter 70(assuming that the shutter 70 is rectangular). By moving liquid to thecorner of the shutter 70, the liquid is accumulated into a larger massand thus can be more easily collected by the liquid recovery portion 42.In addition, the corner of the shutter can be provided with a notch ortaper to further assist in removal of liquid from below the corner ofthe shutter 70.

FIG. 10E shows a preferred process of removing the shutter 70 frombetween the bottom plate 44 of liquid confinement member 18 and thesubstrate 26. It is desirable to quickly move the shutter 70 in order toincrease throughput of the exposure apparatus. However, if the shutter70 is moved too quickly, bubbles can be formed in the immersion liquid29 disposed between the final optical element 16 and the substrate 26.Thus, as shown in FIG. 10E, while the shutter 70 is moved (fromleft-to-right) in FIG. 10E, the substrate 26 also is moved fromleft-to-right. It has been found that moving the substrate and shutterin the same direction during removal of the shutter from the position atwhich it closes the bottom plate aperture 54 reduces the formation ofbubbles between the final optical element 16 and the substrate 26.

The use of the exposure apparatus described herein is not limited to aphotolithography system for semiconductor manufacturing. The exposureapparatus, for example, can be used as an LCD photolithography systemthat exposes a liquid crystal display device pattern onto a rectangularglass plate, or a photolithography system for manufacturing a thin filmmagnetic head.

Semiconductor devices can be fabricated using the above describedsystems, by the process shown generally in FIG. 11A. In step 801 thedevice's function and performance characteristics are designed. Next, instep 802, a mask (reticle) having a pattern is designed according to theprevious designing step, and in a step 803, a wafer is made from asilicon material. The mask pattern designed in step 802 is exposed ontothe wafer from step 803 in step 804 by a photolithography systemdescribed hereinabove in accordance with aspects of the invention. Instep 805, the semiconductor device is assembled (including the dicingprocess, bonding process and packaging process). Finally, the device isthen inspected in step 806.

FIG. 11B illustrates a detailed flowchart example of the above-mentionedstep 804 in the case of fabricating semiconductor devices. In FIG. 11B,in step 811 (oxidation step), the wafer surface is oxidized. In step 812(CVD step), an insulation film is formed on the wafer surface. In step813 (electrode formation step), electrodes are formed on the wafer byvapor deposition. In step 814 (ion implantation step), ions areimplanted in the wafer. The above mentioned steps 811-814 form thepreprocessing steps for wafers during wafer processing, and selection ismade at each step according to processing requirements.

At each stage of wafer processing, when the above-mentionedpreprocessing steps have been completed, the following post-processingsteps are implemented. During post-processing, first, in step 815(photoresist formation step), photoresist is applied to a wafer. Next,in step 816 (exposure step), the above-mentioned exposure device is usedto transfer the circuit pattern of a mask (reticle) to a wafer. Then instep 817 (developing step), the exposed wafer is developed, and in step818 (etching step), parts other than residual photoresist (exposedmaterial surface) are removed by etching. In step 819 (photoresistremoval step), unnecessary photoresist remaining after etching isremoved. Multiple circuit patterns are formed by repetition of thesepreprocessing and post-processing steps.

A photolithography system (an exposure apparatus) according to theembodiments described herein can be built by assembling varioussubsystems in such a manner that prescribed mechanical accuracy,electrical accuracy, and optical accuracy are maintained. In order tomaintain the various accuracies, prior to and following assembly, everyoptical system is adjusted to achieve its optical accuracy. Similarly,every mechanical system and every electrical system are adjusted toachieve their respective mechanical and electrical accuracies. Theprocess of assembling each subsystem into a photolithography systemincludes providing mechanical interfaces, electrical circuit wiringconnections and air pressure plumbing connections between eachsubsystem. Each subsystem also is assembled prior to assembling aphotolithography system from the various subsystems. Once aphotolithography system is assembled using the various subsystems, atotal adjustment is performed to make sure that accuracy is maintainedin the complete photolithography system. Additionally, it is desirableto manufacture an exposure system in a clean room where the temperatureand cleanliness are controlled.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments or constructions. The invention isintended to cover various modifications and equivalent arrangements. Inaddition, while the various elements of the preferred embodiments areshown in various combinations and configurations, that are exemplary,other combinations and configurations, including more, less or only asingle element, are also within the spirit and scope of the invention.

What is claimed is:
 1. An immersion lithography apparatus comprising: asubstrate holder on which a substrate is held; a projection systemhaving a final optical element, the projection system projecting anexposure beam onto the substrate held on the substrate holder through animmersion liquid in a gap between a surface of the substrate and thefinal optical element during an exposure operation; a liquid confinementmember having an aperture through which the exposure beam is projected,the liquid confinement member having a lower surface that surrounds theaperture, the lower surface of the liquid confinement member including anon-fluid removal area that surrounds the aperture, the liquidconfinement member having a liquid recovery outlet from which theimmersion liquid is recovered; and a movable member that is movablerelative to the liquid confinement member in a substantially horizontaldirection, the movable member having an opening through which theexposure beam is projected, the movable member having an upper surfaceand a lower surface that surround the opening, the movable member beingmovable while a portion of the upper surface faces the non-fluid removalarea in the lower surface of the liquid confinement member, wherein theaperture of the liquid confinement member is defined by a radiallyinnermost edge of the non-fluid removal area, and at least a part of theupper surface of the movable member is spaced from the substrate held onthe substrate holder by a shortest distance that is less than a shortestdistance between the substrate and the radially innermost edge of thenon-fluid removal area.
 2. The apparatus of claim 1, wherein the movablemember moves in a same direction as the substrate holder when thesubstrate holder moves the substrate in a direction parallel to thesurface of the substrate.
 3. The apparatus of claim 2, wherein themovable member moves at a speed that is slower than a speed at which thesubstrate holder moves.
 4. The apparatus of claim 3, wherein the movablemember moves by an amount that is less than an amount by which thesubstrate holder moves.
 5. The apparatus of claim 2, wherein the movablemember moves by an amount that is less than an amount by which thesubstrate holder moves.
 6. The apparatus of claim 1, further comprisingan actuator coupled to the movable member to move the movable member. 7.The apparatus of claim 6, wherein the actuator is one of a voice coilmotor and a Lorentz-force actuator.
 8. The apparatus of claim 1, whereinthe movable member includes a plate having the opening.
 9. The apparatusof claim 1, wherein the movable member includes a plurality of platesthat collectively define the opening.
 10. The apparatus of claim 1,wherein the opening is larger than the aperture.
 11. The apparatus ofclaim 1, wherein the movable member is movable to a closing position atwhich the upper surface of the movable member covers the aperture. 12.The apparatus of claim 1, wherein the liquid confinement membersubstantially surrounds the final optical element of the projectionsystem.
 13. The apparatus of claim 1, wherein the movable member isangled.
 14. The apparatus of claim 1, wherein the movable memberincludes a protrusion that extends toward the substrate.
 15. Theapparatus of claim 14, wherein the protrusion is formed along theopening.
 16. The apparatus of claim 1, wherein the liquid recoveryoutlet is provided in the lower surface of the liquid confinementmember.
 17. An immersion lithography apparatus comprising: a substrateholder on which a substrate is held; a projection system having a finaloptical element, the projection system projecting an exposure beam ontothe substrate held on the substrate holder through an immersion liquidin a gap between a surface of the substrate and the final opticalelement during an exposure operation; a first member having an openingthrough which the exposure beam is projected; and a second member havingan opening through which the exposure beam is projected, wherein thefirst and second members are relatively movable in a directionsubstantially parallel to the surface of the substrate, one of the firstand second members has a lower surface, the lower surface includes anon-fluid removal area that surrounds the opening of the one of thefirst and second members, the other of the first and second members hasan upper surface, the first and second members are relatively movablewhile a portion of the upper surface faces the non-fluid removal area inthe lower surface, the one of the first and second members has a liquidrecovery outlet which removes liquid from a gap between the lowersurface and the upper surface, and the opening of the one of the firstand second members is defined by a radially innermost edge of thenon-fluid removal area, and at least a part of the upper surface of theother of the first and second members is spaced from the substrate heldon the substrate holder by a shortest distance that is less than ashortest distance between the substrate and the radially innermost edgeof the non-fluid removal area.
 18. The apparatus of claim 17, whereinthe one of the first and second members has the liquid recovery outletin the lower surface.
 19. The apparatus of claim 17, wherein the liquidrecovery outlet faces a portion of the upper surface when the first andsecond members are relatively moved.